Lift devices are used to move heavy objects from one location to another location. Some lift devices are designed for mounting to a vehicle, such as a truck, and can load and unload objects onto and off of the truck bed. A typical vehicle mounted lift device has a mounting arm connected to the vehicle, a vertical shaft, and a lifting boom with a lift or working head that is secured to the object. The lifting boom can rotate about a horizontal axis with respect to the surface upon which the vehicle is parked. In some designs, the lifting boom is manually rotatable about a vertical axis that is orthogonal to the horizontal axis but to a limited extent, e.g. up to about 90 degrees in total. An example of a manually rotatable lift device is my U.S. Patent Pub. No. 2009/0067968 to McVaugh. Manually rotatable lifting booms exhibit instability during use. For instance, if the object sways substantially, the lift point—the location where the lift device is connected the object—sways out of alignment with the working head of the lifting boom and the vertical axis negatively impacting lifting boom stability during rotation. In situations where the lift device is inclined, gravity forces the object out of alignment with the lift head and can hinder the ability of the lift boom to rotate about the vertical axis in a direction up the incline.